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Quantum Fisher Information as the Convex Roof of Variance

8 Pith papers cite this work. Polarity classification is still indexing.

8 Pith papers citing it
abstract

Quantum Fisher information places the fundamental limit to the accuracy of estimating an unknown parameter. Here we shall provide the quantum Fisher information an operational meaning: a mixed state can be so prepared that a given observable has the minimal averaged variance, which equals exactly to the quantum Fisher information for estimating an unknown parameter generated by the unitary dynamics with the given observable as Hamiltonian. In particular we shall prove that the quantum Fisher information is the convex roof of the variance, as conjectured by Toth and Petz based on numerical and analytical evidences, by constructing explicitly a pure-state ensemble of the given mixed state in which the averaged variance of a given observable equals to the quantum Fisher information.

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years

2026 6 2025 2

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UNVERDICTED 8

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representative citing papers

Enhancing entanglement asymmetry in fragmented quantum systems

cond-mat.stat-mech · 2026-03-02 · unverdicted · novelty 6.0

Entanglement asymmetry for inhomogeneous U(1) charges in fragmented systems scales extensively, is bounded by a universal fraction of its maximum, and distinguishes classical from quantum fragmentation.

Entanglement Requirements for Coherent Enhancement in Detectors

hep-ph · 2026-05-08 · unverdicted · novelty 6.0

Coherent enhancement in detectors is quantitatively constrained by single-mode entanglement entropy, with general bounds on scaling with system size that interpolate between incoherent and fully coherent regimes.

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